When you replaced the cam cover gaskets did you replace the spark plug tube gaskets at the same time?
If not, your old ones in there are hard and leaking. Pretty common.
Cheers
Bennie
Tires are the same. Unfortunately, I threw away the old hub. I plan to call Detroit axle on Monday to ask the difference between a 513303 and a 513220. Maybe it's just the number of N/S poles in the encoder.